The Canadian Northern Cascadia Subduction Zone Observatory (NCSZO), led by Ocean Networks Canada(ONC) has deployed a „Seafloor GPS“ network off Vancouver. Its purpose is to monitor tectonic movements of the Juan de Fuca plate relative to the North American plate.
The core technology of the observatory are 20 Fetch units installed in 400 – 2500m water depth. These Fetch units, supplied by Sonardyne utilise a technique called GPS-A which uses acoustic positioning techniques, inertial navigation, and GPS data to periodically position the Fetch instruments to centimetre-level accuracy, using a Sonardyne transceiver mounted on an unmanned surface vessel. The fetch units themselves are housed in VITROVEX® glass instrument housings secured by protective shells supplied along with the glass spheres.
Image courtesy of David Chadwell